The subject matter of the invention relates to an electrostatic powder coating system, and more particularly to an electrostatic powder coating system which can coat both individual objects and continuous substrates.
Coating materials are applied to a great number of products for aesthetic or functional reasons, by a wide variety of methods and apparatus. Those methods and apparatus have a number of shortcomings. Coating systems utilizing solvents are subject to both the expense of solvents and the expense of disposing of the spent solvents in an environmentally acceptable manner. In hot melt applications or if the viscosity of the coating solutions are raised to decrease solvent usage, other rheology application problems arise.
Apparatus and methods for applying coating material in powder form to a substrate do not suffer from the above shortcomings, however, previous powder coating systems have variously been limited as to the minimum coating thickness which could be applied, the acceptable orientations and adjustability of the apparatus, and the uniformity of the applied coating.
While application methods and devices do exist, current technology is inadequate for applying a continuous, coherent and ultrathin coatings to a large variety of objects. Small objects, such as slugs, often need to be provided with a coating to improve and enhance their function and longevity. One example is metallic objects which are sintered or otherwise formed by powdered metallurgical or ceramic processes. Typical liquid processes encounter high surface tension forces between individual particles of the sintered material causing the liquid to be wicked into the slug or highly porous objects in which the larger pores (representing Faraday Cages) are not adequately coated leaving the exterior surface locally bare in some spots. Additionally, liquid coatings might be totally repelled in certain regions by disabling surface tension forces, such as those regions contaminated with dust, oil or the like. In either case, tiny voids or holidays (defects) in the coating occur, creating potential service problems.
Similarly, while application methods and devices do exist for coating continuous substrates, such as magnet wire, extrusions, strip and sheet materials, and the like, these methods either use relatively large amounts of solvents and are subject both to the expense of solvents and the expense of disposing of the solvents, or are limited by the coating material and the rheology problems associated with that coating material. These methods also have their limitations when ultrathin coatings of less than three (3) microns are desired.
Electrostatic powder coating techniques are also known. However, most of these involve applying the coating to the substrate by passing the substrate through a fluidized bed of particulate coating material. This method requires periodic down time to regenerate the fluidize material in the bed. Such processes also often result in coatings of nonuniform thickness. Uniform thickness depends upon the mobility or flow of the coating material when molten to render the coating uniform, and may not effectively negate gravitational forces on the coating material.
It is therefore highly desirable to provide an improved coating apparatus and method for both continuous substrates and a plurality of discrete objects.
It is also highly desirable to provide an improved coating apparatus and method which applies coatings on both continuous substrates or a plurality of discrete objects disposed in one of a variety of orientations.
It is also highly desirable to provide an improved coating apparatus and method which eliminates the use of solvents.
It is also highly desirable to provide an improved coating apparatus and method which applies continuous, coherent, highly uniform, and ultrathin coatings to substrates or a plurality of discrete objects of a variety of shapes.
It is also highly desirable to provide an improved electrostatic powder coating system which facilitates the application of a continuous, coherent, highly uniform, and ultrathin coatings to both continuous substrates and discrete objects with improved control of film build.
It is also highly desirable to provide an improved coating apparatus and method which is economically efficient and cost effective.
It is also highly desirable to provide an improved coating apparatus and method which utilizes a minimum quantity of coating material per coated object.
It is also highly desirable to provide an improved coating apparatus and method which has a new and improved electrostatic chamber.
It is also highly desirable to provide an improved coating apparatus and method which maximizes the quantity of target objects or substrate area which can be coated within a particular unit of time.
It is also highly desirable to provide an improved coating apparatus and method which has minimal maintenance requirements and yet is operationally efficient.
It is also highly desirable to provide an improved coating apparatus and method which allows for repetitive applications to substrate of different orientations.
It is also highly desirable to provide an improved coating apparatus and method which is capable of coating porous substances, with little surface penetration of the substrate.
It is also highly desirable to provide an improved coating apparatus and method which is economically efficient and cost effective.
Finally, it is highly desirable to provide an improved coating apparatus and method which incorporates all of the above mentioned features.